Electrical connector and apparatus and method for making same



Nov. 10, "1970 D'AS QL. ETAL 3,539,708

ELECTRICAL CONNECTOR AND APPARATUS AND METHOD FOR MAKING SAME FiledMarch 6, 1968 7 l M 9 @MU N 4 8 2 F WWW 2 A 9 7 3 m H r A w A? "'fi''" L3 an A J W 33 8 A 2 2 RL United States Patent 3,539,708 ELECTRICALCONNECTOR AND APPARATUS AND METHOD FOR MAKING SAME Ralph G. DAscoli andLeon L. Alleva, Yonkers, N.Y.,

assignors to Anaconda Wire and Cable Company, a

corporation of Delaware Filed Mar. 6, 1968, Ser. No. 710,944 Int. Cl.H02g 15/08 US. Cl. 174-87 5 Claims ABSTRACT OF THE DISCLOSUREMoisture-tight connectors are made from out lengths of heat-shrinkableplastic tubing by shrinking one end of the tubing around a plasticpellet that softens and bonds to it thus forming a seal. An inwardconstriction is formed in the other end of the tubing by shrinking itover a block that is spaced away from an internal metal sleeve. Theconstriction is needed to retain a dielectric paste with which theconnector is filled.

BACKGROUND OF THE INVENTION This invention relates to electricalconnectors and particularly to connectors suitable for rapidly joiningtwo or more plastic-insulated telephone wires in a moisture-tight,insulated splice.

An understanding of the state of the art prior to our present inventioncan best be obtained by reference to Graff et al. Pat. 3,064,072 andSmith Pat. 3,265,807. These patents describe a type of connector whichhas acquired a widespread commercial usage for splicing telephoneconductors without the need of first stripping off the insulation. Theycomprise a thin-walled, hard-metal shell with inwardly facing prongsthat are capable of piercing the conductor insulation and the outersurface of the conductors themselves. This hard-metal is surrounded by arelatively thick-walled deformable metal sleeve inserted in aninsulating plastic jacket. The ends of conductors which are to beconnected are inserted, together, into the hard-metal shell. The wholeconnector is then compressed by the action of a tool against the outsideof the jacket. The compression is severe enough to deform the deformablesleeve which, in turn, presses together the surfaces of the prongedshell, driving the prongs into the conductors. When the pressure of thetool is released the thick-walled deformed sleeve retains its new shapeand prevents the hard-metal prongs from springing back out-of-contactwith the conductors.

These known types of B-connectors have found their greatest use forpaper insulated telephone conductors. Their application toplastic-insulated conductors has been handicapped by the fact thatctherehas been no known reliable method of making them moisture-tight.

To properly understand this problem it should be understood that costconsiderations require that the plastic jackets of the connectors shouldbe made by chopping up continuous lengths of tubing. This means that theindividual jackets are open at both ends. One end must remain open forinserting the conductors to be spliced, and any sealing of the other endmust be such that large numbers of connectors can be sealedautomatically and economically, at the same time retaining a high degreeof reliability for the moisture-tightness of the seals. The open end ofthe connector is sealed by means of a pasty composition, with which theconnector is filled as described in DAscoli Pat. 2,906,810. Thispatented connector, however, has not proven commercially successfulbecause of the cost of the plug used to prevent compound from pressingout of the open end, and in any event was not intendice ed for thepiercing insert type of B-connector. In the practical use of B-connectortype splices the overriding consideration concerns the time spent by themen who make the splices in the field. To save their time the connectorsare supplied to them factory-filled with waterrepellent composition,such as the composition described in DAscoli and Alleva application Ser.No. 705,322, filed Feb. 14, 1968. The ends of the conductors to bespliced are inserted into the open end of the connector pushing asidethe compound, and entering into the pronged shell. The connector is thencompressed, piercing the insulation, and extruding compound back alongthe conductors. The connectors cannot, practically, be entirely filledwith compound, for in that case, the excess compound from many hundredsof splices that might be made at one time would creat an untidycondition and slow up the splicing operation. Only enough compoundshould be originally included in the connector to fill it after it hasbeen compressed. There is a tendency, however, for the compound tochannel when it is extruded backward during the compression of thesplice and not to fill all the vacant space at the end of the connector.This has even resulted in having the compound squirt in a narrow streamentirely out of the connector, leaving channels free for the ingress ofmoisture.

In the commercial manufacture of B-connectors the tubular insulatingjacket is formed of a heat-shrinkable substance such as polyethylene orpolyvinyl chloride that is shrunk down over the metal sleeve by heatingin an oven or similar means. The resulting open-ended connector has beenquite satisfactory where moisture-tightnes was not required. When,however, as in the present case it is desired to make the connectorsmoisture-tight by filling them with an appropriate composition itbecomes necessary to seal one end of the jacket to prevent loss of thecomposition when the connector is compressed. No economically acceptablemeans for sealing one end of B-connectors has been discovered prior toour present invention.

SUMMARY We have invented improvements in connectors of the typecontaining a dielectric compound and comprising a pressure deformablesleeve surrounding a plurality of conductors within a tubular plasticjacket that is shrunken down, such as by the application of heat,tightly around the sleeve. In this type of connector the jacket extendsbeyond the sleeve to provide unsupported first and second tubularextensions of the jacket at the ends, and the conductors are insertedinto the first of these extensions, Our improvements comprise a radialconstriction in the first extension deflecting the free flow of compoundfrom the jacket when the sleeve is deformed and a pellet of sealantwithin the second extension. The pellet fits easily into the secondextension of the jacket in its preshrunk condition and fills the area inthe shrunken condition. The pellet softens into the shape of theextension at the heatshrinking temperature and bonds to the jacket atthat temperature thereby forming a moisture-tight seal of the extension.

We have invented an apparatus for forming a connector of the typedescribed above comprising a base, a stretcher block mounted on the baseand a pin projecting upwardly centrally from the base. The stretcherblock has a horizontal section approximating the section through thedeformable sleeve of the connector and the pin fits within the sleeveand supports it spaced vertically from the block so as to provide a gapbetween the block and the sleeve for the formation of a radialconstriction when the jacket shrinks down tightly on the sleeve and onthe block.

a substantial portion of the block which has approximately the samehorizontal section as the sleeve. We then deposit a heat-deformableplastic pellet into the upward extension of the tubing, which we heatsufliciently to shrink tightly around the pellet andthe' sleeve and toform a constriction between the sleeve and the" block. Finally, weinject a pasty dielectric compound into the connector.

An electrical splice made in accordance with our invention willtypically comprise a plurality of insulated conductors, contact meanspiercing the insulating of the conductors and connecting themelectrically, and a deformable sleeve that surrounds the conductors andthe contact means. The sleeve is compressed so as to maintain theelectrical continuity between the conductors and the contact means, anda tubular jacket is shrunk-fit tightly around the sleeve. The jacket hasfirst and second tubular extensions beyond the sleeve with theconductors entering through the first extension. The second extension issealed with a plastic plug such as a plug of ethylene ethyl-acrylatecopolymer that bonds to the jacket, such as a polyethylene jacket. Apasty dielectric compound fills the connector, preferably one that willwet the conductor insulation, such a polyethylene insulation, and alsothe jacket material. To help retain the compound the first extension ofthe jacket has a radial construction with an open area greater than thecombined sectional areas of the insulated conductors but less than thetransverse section of the sleeve.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows, in section, a splice madeto our invention.

FIG. 2 shows an apparatus of our invention.

FIGS. 3 and 4 show, in section, successive steps in the method of ourinvention employing the apparatus of FIG. 2.

FIGS. 5, 6, 7 show respectively the steps of filling our connector,inserting the conductors and deforming the sleeve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 a splice,indicated generally by the numeral 10' shows a pair of conductors 11, 12comprising wires 13, 14 covered by walls of polyethylene insulation 16,17 connected electrically and protected from moisture and from outsideelectrical contact by means of a connector indicated generally, by thenumeral 18. Although the insulation on the conductors 11, 12 is solidpolyethylene which is most commonly used for plastic telephone conductorinsulation it will be understood that our invention is in no wiselimited to this particular plastic. Foam or expanded plastic insulationsuch as foam polyethylene and polypropylene and other plastics such asvinyls and ethylene copolymers, and, indeed, many others will haveapplications for our connector and method. The conductors 11, 12 havebeen inserted into a hard bronze shell 19 with inwardly facing prongs 21that have pierced the walls of insulation 16, 17 and made electricalcontact with the conductors 13, 14 thereby connecting these conductors,electrically, to each other. A deformable brass sleeve 22 surrounds thebronze shell 19. The sleeve 22 is closed at one end 23. The features sofar described are all known, as is a jacket 24 shrunk down on the sleeve22. Shrinkable tubing of polyethylene and of polyvinyl chloride iscommercially available, cutinto lengths 26 (FIG. 3) for covering thesleeve 22. It will be understood moreover that the use of such cutlengths of tubing isso much more economical than molded or pressed,closed-end jackets that their use may be considered competitivelyobligatory. The connector structure so far described, however, has beencommercially used mainly for paper-insulated conductors and other caseswhere there has been no need or possibility of securing amoisture-tight,insulated splice. T o render the splice moisture-tight we have filledthe connector 18 with a compound 27 that not only has high dielectricstrength but will wet the surface of the metals and of the polyethyleneinsulation 16, 17 and polyethylene jacket 24. The compound 27 must also,of course, be water repellent and a suitable compound is disclosed inDAscoli Pat. 2,914,501 and in application Ser. No. 705,322. In order tobe able to insert soft copper conductors of small size such as size 24AWG into a connector that contains compound the compound cannot be toostiff and we have now found it desirable to use the lower molecularweights of the rangesof polyethylene disclosed in the above patent toreduce the stiffness of the compound which although it is paired orinjected into the connector hot is cold at the time it is used to make aconnection and the conductors are inserted. The connectors so fardescribed, with the exclusion of the compound filling, are known as aB-connector and a splice is made with such a connector by compressing itbetween anvils 28, 29' of a tool.

This compression not only drives the prongs 21 through the insulation ofthe conductors but it deforms the relatively heavy wall of the sleeve 22which retains its deformed shape indefinitely. The compression, however,would tend to extrude or squirt the compound 27 from the connector ifthe ends were left open. These ends comprise an extension 31 of the tube26 remote from the conductors and an extension 32 through which theconductors enter. We have discovered that the extension 31 can bepermanently sealed at very low cost by means of a plug 33 of a plasticmaterial that will bond to the jacket when the latter is shrunk downaround it, and preferably itself deform somewhat at the shrinkagetemperature to assure the exact shape of a channel 34 that is left inthe extension 31 after it shrinks. In commercial practice the shrinkingof the tube 31 may be done as a batch process by placing a largeplurality of the tube-covered sleeves in an oven, or it may becontinuous with the individual connectors passing through an oven on aconveyor. In either method of shrinking, the plug 33 can beintroduced'into the extension 31 as a pellet 36 (FIG. 3) of a suitableplastic and requires no extra operation to seal the jacket 34, since theshrinking process also effects the sealing, as shall be seen. Anymaterial that will bond to the jacket stock can be employed for thepellet 36 provided that it has the required dielectric and moistureresistant properties and is not adversely affected by the temperature ofshrinking. We have found, however, that the copolymer of ethylene andacrylic acid containing about 8% of the acid and having a melt index,using ASTM Method D1238, of 5, is particularly suitable for forming thepellet 36. Suitable commerial products are known as Dow Zetaphin 70,available from The Dow Chemical Company and Union Carbide 6169 availablefrom Union Carbide Corporation.

The pellet 36 forming the plug 33 adequately seals the extension 31 ofthe jacket 24- but it has been found that when the connector iscompressed by the jaws 28, 29 the compound 27 will still squirt out ofthe extension 32in such a manner as to leave channels for the admissionof moisture. Unexpectedly, however, we have discovered that, if a radialconstriction ordepression 37 is formed in the extension 32, extrusion orsquirting of the compound will be deflected or hindered suificiently toprevent channelling, as we have proven by immersion tests, to bedescribed. The opening within the constriction 37 must be large enoughto permit the easy insertion of the conductors 11, 12, and we have foundthat if this constriction is about the size, or just a little smaller,than the inside opening of the sleeve 22, it will provide the requireddegree of deflection of the compound 27.

We have found, further, that the formation of the constriction 37 can beformed in a surprisingly efficient manner by means of a block 38 (FIGS.24) surmounted by a pin 39 of a proper height. The pin 39 fits into thesleeve 22, actually into the shell 19, and supports the sleeveshellassembly at the end 23 of the sleeve so as to leave a gap 41 between theend of the sleeve 22 and the top of the block 38. This block has aboutthe same horizontal area as a section through the sleeve 22. The tube 26is placed over the sleeve 22 supported on the pin 39 so as to extendacross the gap 41 over the block 38. The pellet 36 is dropped into thetop of the sleeve and the tube is heated for about 2 minutes at 300 F.after which it assumes the shape of the jacket 24 (FIG. 4) closelygripping the sleeve 22 and shrunk above the block 38 to form theconstriction 37. A consideration of typical dimensions of the connector18 will aid in understanding, but other dimensions will, of course,still come within the scope of our invention. For use to connect 2polyethylene-insulated 24 AWG telephone wires a connector about 1% inchlong will comprise a sleeve 22 about inch with an outside section of.205 x .140 inch. For shrinking this connector the gap 41 is about inch.In FIGS. 5-7 we have shown the succeeding steps of introducing thecompound 27 by means of a syringe 41, inserting the conductors 11, 12 tobe connected, and compressing the connector over the conductor. Manymillions of telephone conductor splices must be made each year so thatit will be readily understood that much eflfort has been expended toachieve a practical moisture-tight splice, yet up to the presentinvention this effort has not been successful. In order to test theconnections described herein tests were conducted over an extendedperiod.

EXAMPLE 1 Ten splices were aged for two days at 100 C. and submerged inwater for two hours. All splices showed infinite insulation resistancebetween the conductors and the water on a 600-volt megger.

EXAMPLE 2 Ten splices were aged for seven days at 80 C. and submerged inwater for two hours. All splices showed infinite insulation resistancebetween the conductors and the water on a 600-volt megger.

EXAMPLE 3 Ten splices were aged for thirty days at 70 C. and submergedin water for two hours. All splices showed infinite insulationresistance between the conductors and the water on a GOO-volt megger.

The splices of Examples 1, 2, and 3 were all prepared in accordance withFIG. 1 using the apparatus of FIG. 2 as described hereinabove for thepreferred embodiment of our invention, and were filled with acomposition of mineral oil, polyethylene, petroleum resin and dioctylsebacate described in application Ser. No. 705,322, above mentioned.

We have invented a new and useful connector and apparatus and method formaking the same, of which the foregoing description has been exemplaryrather than definitive and for which we desire an award of LettersPatent.

We claim:

1. In a connector of the type containing a dielectric compound andcomprising a pressure deformable sleeve for surrounding a plurality ofconductors within a tubular plastic jacket, said jacket being heatshrunken down tightly around said sleeve at a preselected temperatureand extending beyond said sleeve to provide unsupported first and secondtubular extensions of said jacket at the ends thereof, said conductorsbeing insertable into a first of said extensions, the improvementcomprising: 7

(A) a pellet of sealant within said second extension,

(a) said pellet fitting easily into said second extension in thepreshrunk condition of said extension,

(b) said pellet filling the area of said second extension in theshrunken condition of said second extension,

(c) said pellet softening into the shape of said extension at saidheat-shrinking temperature, and

(d) said pellet being bonded to said jacket at said temperature therebyforming a moisture tight seal of said second extension.

2. The connector of claim 1 comprising a radial constriction in saidfirst extension, said constriction extending inwardly beyond said sleeveand deflecting the free flow of compound from said jacket upon thedeformation of said sleeve.

3. The connector of claim 1 wherein said pellet comprises a copolymer ofethylene and acrylic acid and said jacket comprises a plastic selectedfrom the group consisting of polyethylene and polyvinyl chloride.

4. An electrical splice comprising (A) a plurality of insulatedconductors,

(B) contact means piercing the insulation of said conductors and makingelectrical connection therebetween,

(C) a deformable sleeve surrounding said conductors and said contactmeans, said sleeve being compressed so as to maintain electricalcontinuity between said conductors and said contact means,

(D) a tubular plastic jacket shrunk-fit tightly around said sleeve andhaving first and second tubular extensions beyond said sleeve, saidconductors entering through said first extension,

(E) a solid plastic plug sealing said second extension,

said plug bonding to said jacket,

(F) a pasty dielectric compound filling said connector,

(G) a radial constriction in said first extension,

(a) said constriction having an open area greater than the combinedsectional areas of said insulated conductors, and

(b) smaller than the transverse section of said sleeve.

5. The splice of claim 4 wherein said conductors are insulated withpolyetheylene, said jacket comprises polyethylene, and said plugcomprises a copolymer of ethylene and ethyl acrylate.

References Cited UNITED STATES PATENTS 2,823,250 2/ 1958 OKeefe 174--873,265,807 8/1966 Smith 17487 3,288,914 11/1966 Fuller et al 174843,320,355 5/1967 Booker 174-87 XR DARRELL L. CLAY, Primary Examiner US.Cl. X.R.

